Peroxides are known bleaching agents. They can be supplied as hydrogen peroxide itself, or by using a hydrogen peroxide "generator" such as a perborate, a percarbonate, a peroxyurea compound, persilic acid and hydrogen peroxide adducts of pyrophosphates, citrates, sodium sulfate and sodium silicate. Such generators readily release hydrogen peroxide in aqueous solution.
However, such peroxides achieve only moderate bleaching when used by themselves in an aqueous environment. Better results have been achieved when they are used with activators. See e.g. U.S. Pat. Nos. 3,398,096, 4,119,557 and 5,460,747. The disclosure of these patents, and of all other publications referred to herein, are incorporated by reference as if fully set forth herein.
Unfortunately, such activators present their own problems. Some activators are susceptible to storage instability. Others are expensive to produce or are highly toxic. Others provide only minor improvements in bleaching effectiveness.
In unrelated work, it has been determined that a tungstate can catalyze the oxidation of secondary amines with hydrogen peroxide (H. Mitsui, J. Chem Soc. Chem. Comm. 874 (1984)), and that an in acid environment certain tungsten containing compounds used with peroxides can help process pulp (U.S. Pat. No. 4,427,490).
However, hard surface stains in buildings and on materials to be used for manufacturing are often caused by mold/fungus, and such stains can be resistant to bleaching by acidic cleaners. Similarly, stains on non-woven and woven textiles can be resistant to bleaching by conventional cleaning compositions. Moreover, peroxides can have stability problems during storage, and especially in alkaline environments.
Thus, a need exists for improved activators for use in alkaline peroxide bleaching systems.